1. Field of the Invention
The present invention relates to a variable valve operating control apparatus of an internal combustion engine having a variable valve timing mechanism and a control method thereof.
2. Description of the Related Art
In Japanese Unexamined Patent Publication 2000-087769, there is disclosed an variable valve operating control apparatus which has a variable valve timing mechanism which varies a rotational phase of a camshaft with respect to a crankshaft of an internal combustion engine, and a variable valve lift mechanism which varies a lift of an engine valve.
In a conventional art, a rotational phase adjusted by a variable valve timing mechanism is detected on the basis of a interval between a detection signal at a reference rotational position of a crankshaft and a detection signal at a reference rotational position of a camshaft.
Then, the aforementioned variable valve timing mechanism is feedback-controlled on the basis of a detected rotational phase on the basis of the interval.
Therefore, there has been the problem that the feedback control of a rotational phase cannot be carried out when a sensor detecting the reference rotational positions breaks down.
Further, in the structure in which a rotational phase is detected on the basis of the detection signals of the reference rotational positions, a rotational phase is detected at every constant crank angle.
Therefore, if an updating period of a rotational phase is made long because of the time when an engine speed is low, a large deviation is generated between a detected value of the rotational phase and an actual value during the updating period.
For example, when a centric phase of an operating angle of an intake valve is made to vary by the variable valve timing mechanism while varying a lift of the intake valve, a variation of increase and decrease in an air quantity with respect to a variation of the centric phase becomes large at the time of low lift.
Therefore, when a rotational phase at a side which is further advance side than an actual angle is detected due to a delay in updating the rotational phase when the rotational phase is being varied in the retard direction, the rotational phase is controlled to be excessively at the retard side. Then, if the rotational phase is excessively set at the retard, a cylinder intake air quantity is increased beyond a request.
Moreover, when an operating angle/a lift of an engine valve are made variable, the maximum operating angle/the maximum lift which can prevent the interference between a piston and the engine valve are different in accordance with a centric phase of the operating angle.
Therefore, when there is a delay in detecting a centric phase, the maximum operating angle/the maximum lift are wrongly set, and as a result, there is a concern in which the mechanism may be controlled so as to be an operating angle/a lift by which the piston and the engine valve interfere with one another.